Biological Suppression of Mealybugs, Coccidohystrix insolitus and Maconellicoccus hirsutus on Hibiscus rosa-smensis

摘要

The impact of naturally occurring lycaenid predator, Spalgis epeus Westwood on Coccidohystrix insolitus (Green) and release of Australian ladybird beetle, Cryptolaemus montrouzieri Mulsant in the suppression o/Maconellicoccus hirsutus (Green) on hibiscus was determined. C. montrouzieri was released @ 20 grubs/plant in March 2003 on hibiscus. The population of pink hibiscus mealybug M . hirsutes declined from 84.3/plant (4 shoots) on 5th March 2003 to 0.9/plant on 12 th May 2003. In another study, a mean of 145.6 mealybugs (C. insolitus) was observed on 15th February 2003, and the mealybug population declined to 0.6/plant on 10th April 2003. In the present investigations, a mean of 99.6%, and 99.0% reduction in the population of C. insolitus and M. hirsutus, respectively was recorded within 60 days of appearance of S. epeus or release of Cryptolaemus on hibiscus. The predators, S. epeus and C. montrouzieri were found feeding on C. insolitus and M. hirsutus, respectively throughout the study period.Moreover, no other natural enemy was recorded on these mealybugs in hibiscus in the present study. Influence of weather factors like temperature, humidity and rainfall on the mealybug population was found to be non- significant . Hence, reduction of mealybugs was attributed mainly to the action of predators S. epeus and C. montrouzieri.